CN112142258B - Resource and standard treatment method for domestic sewage of villages and towns - Google Patents

Abstract

The invention belongs to the field of sewage treatment, and relates to a method for treating domestic sewage in villages and towns, which is carried out in a sewage treatment system comprising an anaerobic digestion tank, a reuse tank, a grid sedimentation tank, an adjusting tank, a variable process biochemical tank, a sedimentation tank and a variable process ecological filter bed, and comprises the following steps: s1, when the liquid level of black water in an anaerobic digestion tank is lower than an overflow limit liquid level, operating in a quality-divided treatment mode, recycling the black water as a high-efficiency liquid fertilizer after anaerobic digestion, and treating grey water to reach the standard and discharging the grey water; s2, when the resource recycling demand of the black water is reduced, the liquid level of the black water in the anaerobic digestion tank is continuously increased to the overflow limit liquid level, and the black water is merged into the grey water treatment system and is switched into a combined treatment mode. The invention realizes the recycling of nitrogen, phosphorus and potassium resources of domestic sewage of villages and towns on site preferentially, thoroughly changes the conventional sewage treatment mode of nitrogen and phosphorus removal, can really realize the recycling of the resources and greatly reduces the treatment cost of the sewage.

Description

A method for resource utilization and up-to-standard treatment of domestic sewage in villages and towns

technical field

The invention belongs to the field of sewage treatment, and in particular relates to a method for resourceful and up-to-standard treatment of domestic sewage in villages and towns.

Background technique

Domestic sewage in villages and towns mainly includes black water and gray water. Among them, black water refers to the effluent of septic tanks. The content of nitrogen, phosphorus and potassium in black water is very high. It is difficult and costly to treat nitrogen and phosphorus pollutants to meet the discharge standards, and it causes a great waste of resources. Gray water is a general term for domestic miscellaneous water, including but not limited to bathroom drainage, kitchen drainage, laundry table drainage, sink drainage, washing machine drainage, garden cleaning drainage and other domestic wastewater other than septic tank effluent. The concentration of pollutants such as phosphorus is low, causing less pollution to the environment, and it is also easier to handle.

At present, for the treatment of domestic sewage in villages and towns, affected by the traditional collection mode, the septic tank effluent, bathroom drainage and kitchen drainage and other domestic wastewater are mixed and collected at the source of sewage generation (that is, black water and gray water are mixed and collected), Then it is transported to the end through the pipe network for carbon, nitrogen and phosphorus removal. However, although this traditional treatment mode can effectively remove pollutants such as organic matter and nitrogen and phosphorus nutrients from sewage, it has the disadvantages of high energy consumption, high cost, and by-products such as residual sludge that are likely to cause secondary pollution to the environment. Secondary pollution and irreversible loss of resources such as carbon, nitrogen, phosphorus, and potassium. From the perspective of the entire life cycle of the sewage treatment system, the cost of pollution control is very high, which will bring a great burden to the environment. With the full popularization of high-speed rail in my country, vacuum toilets on high-speed rail are gradually moving towards the field of sewage treatment. At present, many scientific research institutes and environmental protection companies have developed negative pressure collection systems or equipment for feces and even sewage and applied them The field of sewage treatment, including village and town sewage, has exerted the efficiency and effect that the traditional gravity collection pipe network does not have, but there are many realities in the negative pressure collection system, such as a large number of equipment, high manufacturing and installation requirements, high follow-up operation and maintenance intensity, and high management costs. Problems have severely limited the popularization and application of this technology. Therefore, in order to reduce the difficulty and cost of sewage treatment in villages and towns, there is an urgent need for a resource-based and standard-compliant treatment method that is different from the existing collection and treatment models.

Contents of the invention

The invention aims to provide a novel treatment method for resource utilization and up-to-standard treatment of domestic sewage in villages and towns.

Specifically, as shown in Figures 1 to 3, the present invention provides a method for treating domestic sewage in villages and towns, wherein the method is carried out in a sewage treatment system, and the sewage treatment system includes an anaerobic digestion tank, a reuse pool , grid sedimentation tank, regulating tank, variable process biochemical tank, sedimentation tank and variable process ecological filter bed, the anaerobic digestion tank includes at least two interconnected reaction compartments and the last reaction compartment is at the height of the pool The middle and lower part of the tank is connected with the middle and lower part of the reuse pool so that the anaerobic digester has a certain water volume and water quality regulation capacity during operation. The variable process ecological filter bed includes interconnected water distribution tanks and crushed stone packing filter beds , the water inlet of the first reaction compartment in the anaerobic digestion tank is connected to the black water source, and the water inlet of the grid sedimentation tank is connected to the gray water source; the specific steps include:

S1. When the liquid level of the black water in the anaerobic digester is lower than the limit liquid level of the overflow, the sewage treatment system operates in the mode of resource separation:

The black water flows from the first reaction compartment into the anaerobic digestion tank for anaerobic digestion treatment. The macromolecular organic matter and organic nitrogen and phosphorus in the black water are decomposed into organic acids, inorganic nitrogen and inorganic phosphorus, and then discharged into the reuse tank As a liquid fertilizer rich in organic acids and nitrogen, phosphorus and potassium, it is used for agricultural, forestry and vegetable fields; the gray water passes through the grid sedimentation tank to remove quicksand, suspended solids and floating solids, and then flows into the regulating tank to adjust the fluctuation and change of water volume and water quality. Then it is lifted by the water pump into the variable process biochemical pool, sedimentation tank and variable process ecological filter bed. The contact oxidation (aerobic) mode introduced at the front end of the biochemical pool treats gray water, removes organic matter (COD) and ammonia nitrogen in gray water, and the variable process ecological filter bed is filled with gravel (that is, traditional horizontal subsurface flow wetland) The model further treats the gray water after biochemical treatment to further remove COD, ammonia nitrogen, total nitrogen and total phosphorus. Before the gray water enters the variable process ecological filter bed, it needs to enter the sedimentation tank for sedimentation treatment to realize the separation of mud and water. After the sedimentation treatment, the remaining sludge is discharged into the black water anaerobic digestion tank for anaerobic digestion treatment, so that the excess sludge is reduced and the nitrogen and phosphorus nutrients in the microorganisms are released, and the water after the sedimentation treatment flows into the distribution tank in turn and gravel packed filter bed;

S2. When there is no need for reuse of black water for a long time, the liquid levels in the black water anaerobic digestion tank and the reuse tank will continue to rise to the overflow limit level synchronously under the condition of continuous water inflow, and the black water will start from The water inlet automatically overflows to the gray water adjustment tank, and the domestic sewage at this time will be operated in the combined standard treatment mode:

The black water that continues to enter the anaerobic digestion tank overflows directly from the water inlet of the first reaction compartment into the (gray water) regulating tank, and the black water in the anaerobic digestion tank will still be treated according to the steps of S1; the gray water passes through the grille After removing quicksand, suspended matter and floating matter in the sedimentation tank, it is introduced into the regulating tank, mixed with the overflow black water in the regulating tank, and then lifted by the water pump into the variable process biochemical tank, sedimentation tank and variable process ecological filter bed. Under the standard treatment mode, the variable process biochemical pool operates in a series mode of "aerobic + multi-stage anoxic/aerobic" ("O+multi-stage A/O") with multi-point water inflow to remove COD, Ammonia nitrogen and total nitrogen; the variable process ecological filter bed operates in the mode of enhanced phosphorus removal filter bed to treat the mixed sewage after biochemical treatment, mainly to remove the total phosphorus in the mixed sewage, and can deeply remove the COD in the mixed sewage , ammonia nitrogen and total nitrogen, so that the effluent reaches the corresponding discharge standards; the mixed sewage needs to enter the sedimentation tank for sedimentation treatment before entering the variable process ecological filter bed to realize the separation of mud and water, and the remaining sludge after sedimentation treatment is discharged into (black Anaerobic digestion treatment is carried out in the anaerobic digestion tank to reduce the excess sludge and release the nitrogen and phosphorus nutrients in the microorganisms. The water after the sedimentation treatment flows into the water distribution tank and the crushed stone filter bed in turn.

Further, the COD concentration in the black water is 150-650 mg/L, the ammonia nitrogen concentration is 130-230 mg/L, the total phosphorus concentration is 3-20 mg/L, and the potassium ion concentration is 100-300 mg/L.

Further, the gray water has a COD concentration of 50-80 mg/L, an ammonia nitrogen concentration of 5-10 mg/L, a total nitrogen concentration of 5-15 mg/L, and a total phosphorus concentration of 0.2-0.5 mg/L.

Further, when the combined standard treatment mode is adopted, the influent COD concentration of the mixed sewage of black water and gray water is 100-300mg/L, the concentration of ammonia nitrogen is 35-90mg/L, and the concentration of total nitrogen is 35-100mg/L. The total phosphorus concentration is 0.5-10mg/L.

Further, the filling height of the biochemical filler in the anaerobic digester accounts for 40-60% of the effective height of the anaerobic digester.

Further, the upper, middle and lower positions of the anaerobic digester are connected through holes or pipes, but the height of the holes or pipes is preferably consistent with the top of the biological filler.

Further, in the quality-by-substance recycling mode and the combined standard-reaching treatment mode, the treatment conditions of the anaerobic digestion tank include a temperature of 10-40° C. and a hydraulic retention time of 15-30 days.

Further, the variable process biochemical pool has the function of switching different process operations, which includes N-level reaction units, N≥2, and each level of reaction units is equipped with aeration pipe networks and biological fillers, which can be recycled according to the quality of resources. Or combine the standard treatment mode to change the aerobic or anoxic state of the reaction unit. In the sub-substance recycling mode, all the reaction units operate in the contact oxidation (that is, aerobic) mode. Multi-stage anoxic/aerobic” series mode operation, the front end of the first aerobic zone and the anoxic zone at all levels are equipped with water inlets, the flow is controlled by the water inlet pump, the sewage flows from the first aerobic zone and the anoxic zone at all levels The effluent from the variable process biochemical tank flows into the sedimentation tank.

Further, the fillers installed in each aerobic zone and anoxic zone are belt-type fillers and aeration devices.

Furthermore, when the quality-based resource utilization mode is adopted, all the aeration devices in the variable process biochemical tank are turned on, and the gray water from the regulating tank is introduced from the front end of the variable process biochemical tank, and flows through each area in a push flow state, Flows from the last stage and flows into the sedimentation tank.

Further, when the combined standard treatment mode is adopted, the aeration devices in each area of the variable process biochemical pool are operated in the order of "open-close-open-close-open...", so that the variable process becomes "O+more The mixed sewage from the adjustment tank is introduced from the front end of the first aerobic zone and the front end of the anoxic zone at each level, and flows through each zone in a push flow state, starting from the last aerobic zone. The area flows out and flows into the sedimentation tank, and a reflux pump is installed in the last-stage aerobic area to improve the denitrification rate of the biochemical system in the combined standard treatment mode, and the final-stage nitrification solution is returned to the last-stage anoxic area, and the return ratio 100-300%.

Furthermore, when the combined treatment mode is adopted, the influent flow distribution coefficient ri of each level satisfies the following two formulas: [1] r ₀ +r ₁ +r ₂ +···r _n =1(n≥1), 【2】r _n ＝(a/b) ⁿ r ₀ , a is the amount of COD required to reduce 1 mg/L NO ₃ -N to N ₂ (COD unit is mg/L), b is influent COD/ TN concentration ratio.

Further, when the quality-based recycling mode is adopted, the treatment conditions of the sewage in the variable process biochemical tank include a temperature of 10-40°C and a hydraulic retention time of more than 4h.

Further, when the combined standard treatment mode is adopted, the treatment conditions of the sewage in the variable process biochemical tank include a temperature of 10-40° C. and a hydraulic retention time of more than 12 hours.

Furthermore, under the mode of resource separation by quality and combined standard treatment mode, the hydraulic retention time of sewage in the water distribution tank of the variable process ecological filter bed is more than 0.5h, and the hydraulic retention time of the crushed stone packing filter bed is 10h above.

Further, when adopting the quality-based recycling mode, there is no need to add phosphorus removal filter material packs to the water distribution tank of the variable process ecological filter bed with the function of switching different process operations; when adopting the combined treatment mode, it is necessary to switch Phosphorus removal filter packs are added to the water distribution tank of the variable process ecological filter bed with different process operation functions. The phosphorus removal filter bag is composed of water supply sludge, lime, sea oyster shell and iron salt and aluminum salt coagulant wrapped in a water-permeable cloth bag.

Further, the gravel-filled filter bed adopts a design of more than two stages, but preferably a two-stage design, the direction of water flow is up and down, and no soil is covered, and canna, chrysanthemum, windmill grass and mushroom grass are planted as wetland green plants.

The beneficial effects of the present invention are as follows:

(1) Prioritize the recycling of nitrogen, phosphorus and potassium resources in the domestic sewage of villages and towns, completely change the conventional sewage treatment mode of nitrogen and phosphorus removal, truly realize the recycling of resources, and greatly reduce the treatment of sewage in villages and towns, especially in rural areas cost.

(2) Under the resource-based mode, black water can be reused as high-efficiency organic liquid fertilizer after treatment, and will not pollute the environment; after gray water is treated, COD, ammonia nitrogen, total nitrogen and total phosphorus can reach The first-class A discharge standard is discharged, and the remaining sludge generated in the gray water system is discharged into the black water system for anaerobic digestion, without sludge treatment and disposal.

(3) Under the combined standard treatment mode, black water enters the gray water treatment system to be mixed with gray water for treatment, and the gray water treatment system is switched to an efficient denitrification and phosphorus removal mode to ensure that the effluent COD, ammonia nitrogen, total nitrogen and total phosphorus are stable. Tier 1 A emission standards, so as to achieve the effect of "covering the bottom line" and meeting the emission standards.

(4) Whether it is the quality-based recycling model or the combined standard treatment model, chemical phosphorus removal is not required, so there is no treatment and disposal of phosphorus-containing chemical sludge, and no secondary pollution will be caused. The treatment cost of the combined treatment mode is also lower than that of the conventional nitrogen and phosphorus removal process.

Description of drawings

Fig. 1 is the processing flow diagram of black water under the quality resource utilization mode;

Fig. 2 is the processing flow diagram of gray water under the mode of resource utilization by quality;

Fig. 3 is a processing flow chart in the merger compliance processing mode.

Detailed ways

Black water: The excrement from flushing the toilet is discharged into the septic tank, and the effluent of the septic tank is black water. The content of nitrogen, phosphorus and potassium in the black water is very high. It is difficult and costly to treat the nitrogen and phosphorus content in the black water to meet the discharge standard. high.

Greywater: A general term for miscellaneous domestic water, including but not limited to bathroom drainage, kitchen drainage, laundry counter and sink drainage, washing machine drainage, and yard cleaning drainage, excluding septic tank effluent.

The black water or gray water mentioned in this scheme does not include roof or surface rainwater.

The invention separately treats the gray and black separated village and town domestic sewage according to its water quality characteristics. The source of black water is the effluent from the septic tank, which is collected through special pipes. The source of gray water is all kinds of miscellaneous domestic water except septic tank effluent, which is collected through special pipelines.

The core of the present invention is a set of two operating modes of the system, that is, the quality-based resource mode and the merged and up-to-standard processing mode. During the cultivation season of agricultural, forestry and vegetable fields, the reuse amount of liquid fertilizer increases, and the liquid level of black water in the anaerobic digester is lower than the limit liquid level of the overflow, and the mode of recycling by quality is adopted; in the fallow season of agricultural, forestry and vegetable fields, the liquid fertilizer The reuse amount of the black water decreases, and the liquid level of the black water in the anaerobic digestion tank and the reuse tank continues to rise to the overflow limit level and then overflows, and the combined treatment mode is adopted.

Quality-based resource utilization model: After the gray water is treated by biological contact oxidation, sedimentation and ecological filter bed, SS, COD, ammonia nitrogen, total nitrogen and total phosphorus all reach the first level of "Comprehensive Discharge Standards for Urban Sewage Treatment Plants" (GB18918-2002) Discharge after standard A, and the remaining sludge in the sedimentation tank is discharged into the anaerobic digestion tank for reduction and harmless treatment; the black water enters the reuse tank after 15-30 days of anaerobic digestion and stabilization, and then can be passed through constant pressure frequency conversion The water supply system transports the organic liquid fertilizer (clarified liquid) rich in organic acids and nitrogen, phosphorus and potassium to the agricultural, forestry and vegetable fields as liquid fertilizer for irrigation.

Combined standard treatment mode: in the fallow season of agricultural, forestry and vegetable fields, the reuse amount of liquid fertilizer decreases, and the liquid level of the anaerobic digester with water volume adjustment function will continue to rise to the limit liquid level (overflow port, the overflow port is set at the inlet water end), the black water begins to overflow to the gray water adjustment tank, the overflow port is equipped with a flow meter, and when the flow meter detects that the continuous overflow time reaches the system preset value, the control system will switch the quality-based resource utilization mode to the combined standard The treatment mode, the variable process biochemical pool is changed from the original contact oxidation mode (only the front end of the first-level aerobic zone) to the multi-point water intake "O + multi-level A/O series" high-efficiency and low-consumption denitrification treatment mode ( In the front end of the first-level aerobic zone and the front end of the anoxic zone at all levels), at the same time, the administrator adjusts the water intake ratio of the variable process biochemical pool, and adds phosphorus removal filter to the water distribution tank of the variable process ecological filter bed The phosphorus removal filter material package is composed of water supply sludge, lime, sea oyster shell and coagulant of iron salt and aluminum salt system wrapped in permeable cloth bags, so as to ensure that the effluent COD, ammonia nitrogen, total nitrogen and total phosphorus can all be stabilized to << Comprehensive Discharge Standards for Urban Sewage Treatment Plants (GB18918-2002) Class A Discharge Standards. During the combined treatment, carbon sources can be added to the adjustment pool according to the water quality to improve the nitrogen removal rate. After entering the cultivation period, the amount of black water reuse increases, and the black water no longer overflows. When the black water anaerobic digester has not overflowed for a period of time reaching the system preset value, the control system automatically switches to the mode of resource utilization.

Embodiment The following takes the actual case of domestic sewage treatment in a certain village as an example to expand the description

(1) Design of sewage treatment system: black water volume 20-30m ³ /d, gray water volume 40-70m ³ /d, total sewage volume 60-100m ³ /d.

① Anaerobic digester:

The water inlet is equipped with an open channel flowmeter, equipped with a Pasteur metering tank and an ultrasonic flowmeter.

The overflow port is equipped with an open channel flowmeter, equipped with a Pasteur metering tank and an ultrasonic flowmeter.

The design treatment temperature is 10-40°C, and the hydraulic retention time is 15-30 days.

Volume and size: 520m ³ is needed for daily black water meter of 20m ³ /d. It adopts simple anaerobic digestion process design and operates at normal temperature. The effective size is 25×5×5.5m (length, width and height, net effective size, The same below).

②Reuse pool:

The reuse tank and the anaerobic digester are connected to the digester at the installation height of the filler, so that the reuse tank and the digester have a larger water adjustment volume during use, and ensure that the biological filler in the digester is always submerged in the underwater. A frequency conversion water supply system is installed at the end of the reuse pool as agricultural irrigation equipment in the village. The highest elevation of the farmland in the village is 930m, the elevation of the sewage treatment station is 870m, and the difference between the two is at most 60m. Therefore, it is proposed to use two multistage centrifugal pumps with a lift of 70m, one for use and one for standby, equipped with submerged differential pressure level gauges 1 set, 1 set of rotameter and 1 set of electromagnetic flowmeter, 3 sets of pressure sensors.

The reuse of resources is given priority to the villagers' own use, and the surplus is used for the vineyards outside the village. When the villagers and the vineyards have no demand for use, the gray water will flow into the gray water treatment system for treatment.

③Grille sedimentation tank:

Remove pollutants: quicksand, suspended solids and floating solids in water.

Volume and size: 3m ³ , 5×0.5×1.2m. The quicksand content in the sewage is calculated as 0.3% of the maximum sewage volume, which meets the effective volume of sand storage for at least 7 days, and the sand is cleaned manually on a regular basis. It is equipped with a simple hydraulic grid, one set of thick and thin grids, the material is SUS304, the grid spacing of the coarse grid is 50mm, and the grid spacing of the fine grid is 10mm, and a working distance of 800mm is left in front of each grid for manual cleaning. scum. The outlet of the grit grating pool is equipped with an open channel flowmeter, equipped with a Pasteur metering tank and an ultrasonic flowmeter.

④Adjusting pool

Volume and size: 50m ³ , 10×2.5×2m.

Parameters and requirements: When the maximum gray water volume is 70m ³ /d, the adjustment capacity of the adjustment tank is greater than 16 hours, which can fully meet the daily peak drainage demand. Supporting 2 submersible pumps, one for use and one for standby, automatic rotation, submersible pump rated flow 3m ³ /h, rated head 8m, rated power 0.37kw, equipped with 1 set of submerged differential pressure level gauge. It is equipped with 3 rotameters and 1 set of electromagnetic flowmeter. This project is designed according to 3 points of water intake under the combined treatment mode.

⑤Variable process biochemical pool

Remove pollutants: CODCr, NH ⁴⁺ -N, TN.

Volume and size: 10×2×3.4m (net inner size).

The bottom of the variable process biochemical tank is equipped with a microporous membrane type aeration disc, and a belt type combined filler is installed in the tank.

The variable process biochemical pool includes three-stage reaction units, including O1 pool, A2 pool, O2 pool, A3 pool, and O3 pool connected in sequence. The O1 pool takes 10m ³ , the A2 pool takes 5m, the O2 pool takes 12m ³ , and the A3 pool Take 25m ³ , O3 pool takes 8m ³ , the total effective volume of the variable process biochemical pool is 60m ³ , each pool is equipped with filler and aeration device. Two return pumps are installed in the O3 pool, with a rated flow rate of 9m ³ /h and a head of 10m, equipped with a rotameter and a flow regulating valve group. The aeration devices in each pool are microporous membranes, and Roots blowers are used to blow air. The rated air volume is 0.9m ³ /min, the wind pressure is 34.3KPa, and the rated power is 1.1kw. When gray water is treated separately, all the aeration devices in the variable process biochemical tank are fully turned on, and the gray water from the adjustment tank is introduced into the biochemical tank from the front end of the first aerobic zone, and flows through each zone in a push flow state. The primary anoxic zone flows out and flows into the sedimentation tank; when combined treatment, the aeration device of the variable process biochemical tank is set according to on-off-on-off-on, and the rated air volume of the required fan is 2.04m ³ /min, the source The gray water in the self-regulating pool is introduced into the biochemical pool from the front end of the first-level aerobic zone and the front-end of the anoxic zone at each level, flows through each zone in a multi-point inflow state, and flows out from the last-level anoxic zone and flow into the sedimentation tank.

⑥ Sedimentation tank:

Remove pollutants: SS

Volume and size: 12m ³ , 2×2×3.4m (net inner size)

Parameters and requirements: install inclined pipe packing and a set of sludge discharge electric ball valve, and discharge sludge into the black water treatment system during normal operation.

⑦ Variable process ecological filter bed

Removal of pollutants: SS, CODCr, NH ⁴⁺ -N, TN and TP

The variable process ecological bed removal includes a water distribution pool and a crushed stone packing filter bed. The water distribution pool is also used as an emergency pool for phosphorus removal, and the effective volume is designed according to the hydraulic retention time of not less than 0.5 hours. No phosphorus removal filter bag is added; when combined treatment is adopted, a phosphorus removal filter bag is added to the distribution tank to absorb the total phosphorus in the mixed sewage. The crushed stone filler filter bed goes in and out, and the crushed stone filler is used without soil covering, and wetland green plants such as shiitake mushrooms and cannas are planted. The crushed stone packed filter bed adopts two-stage series design to improve the treatment effect, and the designed hydraulic retention time of the crushed stone packed filter bed is not less than 10h. Wetland water outlets are provided with open channel flowmeters, using Pasteur metering channels and equipped with ultrasonic flowmeters.

The sewage treatment system can be controlled by an automatic control and remote monitoring system. The automatic control and remote monitoring system adopts PLC and touch screen, and is equipped with a remote monitoring system.

(2) The specific process of sewage treatment:

S1. When the liquid level of the black water in the anaerobic digester is lower than the limit liquid level of the overflow, the sewage treatment system operates in the mode of resource separation:

Black water (COD concentration is 150-650mg/L, ammonia nitrogen concentration is 130-230mg/L, total phosphorus concentration is 3-20mg/L, potassium ion concentration is 100-300mg/L) flows into the exhaust chamber by gravity from the first reaction compartment. Anaerobic digestion treatment is carried out in the oxygen digestion tank (temperature is 10-40°C, hydraulic retention time is 15-30 days), and the macromolecular organic matter and organic nitrogen and phosphorus in the black water are decomposed into organic acids, which can promote plant growth, Inorganic nitrogen and inorganic phosphorus are then discharged into the reuse pool as a liquid fertilizer rich in nitrogen, phosphorus and potassium for application in agriculture, forestry and vegetable fields; gray water (COD concentration is 50-80mg/L, ammonia nitrogen concentration is 5-10mg/L, The total nitrogen concentration is 5-15mg/L, and the total phosphorus concentration is 0.2-0.5mg/L) through the grid sedimentation tank to remove quicksand, suspended solids and floating solids, and then flow into the regulating tank to adjust the fluctuation and change of water volume and water quality. Then it is lifted by the water pump into the variable process biochemical pool and the variable process ecological filter bed. Under the materialization treatment and resource utilization mode, the variable process biochemical pool treats gray water in the aerobic mode of the first single-point water intake (temperature is 10- 40℃, the hydraulic retention time is more than 4h), to remove organic matter (COD) and ammonia nitrogen in the gray water, and the variable process ecological filter bed uses the mode of crushed stone packing filter bed (that is, the traditional horizontal subsurface flow wetland) to further treat the biochemically treated Gray water is treated, mainly to remove COD, ammonia nitrogen, total nitrogen and total phosphorus. Before entering the variable process ecological filter bed, the gray water needs to enter the sedimentation tank for sedimentation treatment to realize the separation of mud and water. After the sedimentation treatment, the remaining sludge is discharged Enter the black water anaerobic digestion tank for anaerobic digestion treatment, reduce the excess sludge and release the nitrogen and phosphorus nutrients in the microorganisms, and the water after the sedimentation treatment flows into the water distribution tank and the crushed stone filter bed in turn;

S2. When there is no need for reuse of black water for a long time, the liquid levels in the black water anaerobic digestion tank and the reuse tank will continue to rise to the overflow limit level synchronously under the condition of continuous water inflow, and the black water will flow from the incoming The outlet automatically overflows to the gray water adjustment tank, and the domestic sewage at this time will be operated in the combined standard treatment mode:

The black water that continues to enter the black water digestion tank overflows directly from the inlet of the first reaction compartment into the gray water adjustment tank, and the black water in the black water digestion tank will still be treated according to the steps of S1; the gray water passes through the grid sedimentation tank After removing the quicksand, suspended matter and floating matter in the water, it is introduced into the regulating tank, and mixed with the overflow black water in the regulating tank (the upper limit of the concentration of each pollutant in the designed mixed sewage is respectively 180mg/L of COD concentration, 80mg/L of ammonia nitrogen, 80mg/L of ammonia nitrogen, The total nitrogen is 80mg/L, the total phosphorus content is 8mg/L), and then it is lifted into the variable process biochemical pool, sedimentation tank and variable process ecological filter bed through the water pump. The series mode of water "O+multi-stage series A/O" is operated, the temperature is 10-40°C, and the hydraulic retention time is more than 12h. This project adopts three-point water intake, and the required carbon-nitrogen ratio is 4. The first-stage water intake ratio is 16%, the proportion of water entering the second stage is 30%, and the proportion of water entering the final stage is 54%, so the denitrification rate is 46%, and the total nitrogen concentration in the terminal effluent is 43.2mg/L. In order to ensure that the total nitrogen in the effluent can reach the standard stably, the terminal effluent is returned to A2 for enhanced oxidation, and carbon sources are added to the A2 pool at the same time. If the reflux ratio is 200%, the reflux denitrification rate of A2 is 66%, and the total nitrogen in the effluent can theoretically be From 44mg/L to 15mg/L. After the biochemical treatment, the effluent enters the sedimentation tank for sedimentation treatment to realize the separation of mud and water. After the sedimentation treatment, the remaining sludge is discharged into the black water anaerobic digestion tank for anaerobic digestion treatment, so that the excess sludge is reduced and released into the microbial body Nitrogen and phosphorus nutrients, the supernatant water after sedimentation treatment is discharged into the variable process ecological filter bed operated in the mode of enhanced phosphorus removal for treatment, and the phosphorus removal filter material bag is added to the distribution pool of the ecological filter bed to remove Total phosphorus in the mixed sewage, and can deeply remove COD, ammonia nitrogen and total nitrogen in the mixed sewage, so that the effluent can meet the corresponding discharge standards; the effluent COD concentration of the variable process ecological filter bed is 50mg/L, and the ammonia nitrogen concentration is 5mg/L , the total nitrogen concentration is 15mg/L, and the total phosphorus concentration is 0.5mg/L.

(3) Analysis of operating costs

After calculation and analysis, the unit energy consumption of the separated treatment and combined treatment is [50kwh/d, 0.83kwh/m ³ ] (the divided treatment mode, including recycling energy consumption, accounting for 36%) and [70kwh/d, 1.17kwh/m ³ ] (standard treatment mode, excluding recycling energy consumption).

Compared with conventional rural sewage treatment projects, the quality-based treatment model has obvious advantages in subsequent operation and maintenance expenditures and ecological environment protection, mainly reflected in:

① Staff salary expenditure

Under the traditional treatment mode, phosphorus removal agents need to be dispensed at least once a week, and the increased cost is calculated at 1,000 yuan per month, and an annual increase of 12,000 yuan is required.

②Phosphorus removal agent fee

Under the traditional collection and treatment mode, the average concentration of total phosphorus in the influent will reach more than 5mg/L. Based on the effluent total phosphorus of 0.5mg/L and the sewage volume of 60m ³ /d, it is necessary to add 1 ton of phosphorus removal chemicals throughout the year. , if the phosphorus removal agent is calculated at 5,000 yuan/ton, an increase of 5,000 yuan is required. If we consider maintaining a stable removal rate of TN, the cost of adding carbon sources is expected to increase by 10,000 yuan/year.

③The treatment cost of phosphorus-containing sludge

Due to the small amount of sewage of 60-100m ³ /d, it is not suitable to be equipped with sludge dewatering equipment, and the phosphorus-containing chemical sludge generated should be transported to the nearest municipal sewage treatment plant by fecal suction truck for treatment and disposal. In the present invention, it is assumed that the municipal sewage treatment plant can receive and dispose of the generated wet sludge free of charge, and only the transfer cost of the wet sludge is analyzed.

Under the traditional treatment mode, 2.5m ³ of phosphorus-containing wet sludge will be produced every day, and its moisture content will exceed 99.9%. After concentration, the moisture content can be reduced to 99%. If it is transferred every two weeks, there will be 3.5m ³ For the wet sludge, the transfer fee is calculated at 1,000 yuan per time, and the annual cost is 24,000 yuan.

According to the above analysis, if domestic sewage is collected and treated in a gray-black separation mode, the effluent will stably reach the water quality standard superior to Grade A of the "Comprehensive Discharge Standard for Urban Wastewater Treatment Plants" (GB18918-2002), and it will be directly operated The cost will save more than 51,000 yuan per year compared with the traditional governance model. In addition, about 6,000 tons/year of high-efficiency liquid nitrogen and phosphorus fertilizers will be harvested, which is equivalent to 2,000 kg of urea with an effective amount of TN not less than 45% and 1,375 kg of calcium magnesium phosphate fertilizers with an effective amount of P ₂ O ₅ not less than 12%. Yuan/50kg and calcium magnesium phosphate fertilizer 120 yuan/25kg based on market information, the high-efficiency liquid nitrogen and phosphorus fertilizer produced throughout the year can be equivalent to about 25,000 yuan.

Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be construed as limitations to the present invention. Variations, modifications, substitutions, and modifications to the above-described embodiments are possible within the scope of the present invention.

Claims (10)

1. A treatment method for domestic sewage in villages and towns, characterized in that, the method is carried out in a sewage treatment system with two modes of operation: resource-based treatment and combined up-to-standard treatment, and the sewage treatment system includes an anaerobic digester, Reuse tank, grid sedimentation tank, regulating tank, variable process biochemical tank, sedimentation tank and variable process ecological filter bed, the anaerobic digestion tank includes at least two interconnected reaction compartments and the last reaction compartment The middle and lower part of the pool height is connected with the middle and lower part of the reuse pool so that the anaerobic digester has a certain water volume and water quality regulation ability during operation, and the overflow port of the anaerobic digester with water volume adjustment function is set At the water inlet, the overflow port is provided with a flow meter. The variable process ecological filter bed includes an interconnected water distribution tank and a crushed stone packing filter bed. The water inlet of the first reaction compartment in the anaerobic digestion tank is connected to Black water source, the water inlet of the grid sedimentation tank is connected to the gray water source; The variable process biochemical pool has the function of switching different process operations, which includes N-level reaction units, N≥2, and each level of reaction units is equipped with aeration pipe networks and biological fillers, which can meet the standards according to the resource-based mode or merger The treatment mode changes the aerobic or anoxic state of the reaction unit: in the sub-resource mode, all the reaction units operate in the aerobic mode, and in the combined standard treatment mode, the reaction units operate in the "aerobic + multi-level anoxic/aerobic" mode The series mode operation of the first section of the aerobic zone and the front ends of the anoxic zones at all levels are equipped with water inlets, and the flow is controlled by the water inlet pump. The effluent of the zone is mixed for efficient biological denitrification and denitrification treatment, and the effluent of the variable process biochemical tank flows into the sedimentation tank; The core of the treatment method of domestic sewage in villages and towns is a set of two operating modes of the system, that is, resource-based treatment by quality and combined up-to-standard treatment; Specific steps include: S1. When the liquid level of the black water in the anaerobic digester is lower than the limit liquid level of the overflow, the sewage treatment system operates in the mode of resource separation: The black water flows from the first reaction compartment into the anaerobic digestion tank for anaerobic digestion treatment. The macromolecular organic matter and organic nitrogen and phosphorus in the black water are decomposed into organic acids, inorganic nitrogen and inorganic phosphorus, and then discharged into the reuse tank As a liquid fertilizer rich in organic acids and nitrogen, phosphorus and potassium, it is used for agricultural, forestry and vegetable fields; the gray water passes through the grid sedimentation tank to remove quicksand, suspended solids and floating solids, and then flows into the regulating tank to adjust the fluctuation and change of water volume and water quality. Then it is lifted by the water pump into the variable process biochemical tank, sedimentation tank and variable process ecological filter bed. Under the mode of separation and resource utilization, the variable process biochemical pool treats gray water in the aerobic mode of the first single-point water intake, and removes COD and ammonia nitrogen in gray water, the variable process ecological filter bed further treats the gray water after biochemical treatment in the mode of crushed stone packing filter bed, and further removes COD, ammonia nitrogen, total nitrogen and total phosphorus. Before changing the process to the ecological filter bed, it needs to enter the sedimentation tank for sedimentation treatment to realize the separation of mud and water. After the sedimentation treatment, the remaining sludge is discharged into the black water anaerobic digestion tank for anaerobic digestion treatment, so that the excess sludge is reduced and released Nitrogen and phosphorus nutrients are released from the microorganisms, and the water after sedimentation treatment flows into the water distribution tank and the crushed stone filter bed in turn; Under the quality-based recycling mode, black water can be reused as high-efficiency organic liquid fertilizer after treatment, and will not pollute the environment; after gray water is treated, COD, ammonia nitrogen, total nitrogen and total phosphorus can all reach the first grade A The excess sludge generated in the gray water system is discharged into the black water system for anaerobic digestion without sludge treatment; S2. When there is no need for reuse of black water for a long time, the liquid levels in the black water anaerobic digestion tank and the reuse tank will continue to rise to the overflow limit level synchronously under the condition of continuous water inflow, and the black water will start from The water inlet automatically overflows to the gray water adjustment tank. When the flow meter detects that the continuous overflow time reaches the system preset value, the control system will switch the quality-based recycling mode to the combined treatment mode. At this time, the domestic sewage will be combined and met the standard Processing mode runs: The black water that continues to enter the anaerobic digestion tank overflows from the first reaction compartment into the gray water adjustment tank, and the black water in the anaerobic digestion tank will still be treated according to the steps of S1; the gray water is removed from the quicksand through the grid sedimentation tank , suspended solids and floating solids are then introduced into the regulating tank, mixed with the overflow black water in the regulating tank, and then lifted into the variable process biochemical tank, sedimentation tank and variable process ecological filter bed through the water pump. In the combined standard treatment mode, it can The variable process biochemical pool operates in a series mode of "aerobic + multi-stage anoxic/aerobic" with multi-point water inflow to remove COD, ammonia nitrogen and total nitrogen in the mixed sewage. In the water distribution pool of the variable process ecological filter bed The mixed sewage after biochemical treatment is treated in the mode of strengthening the phosphorus removal filter bed after adding the phosphorus removal filter bag in the medium. Salt coagulant composition; Mainly remove the total phosphorus in the mixed sewage, and deeply remove the COD, ammonia nitrogen and total nitrogen in the mixed sewage, so that the effluent can meet the corresponding discharge standards; the mixed sewage needs to enter the sedimentation tank for sedimentation treatment before entering the variable process ecological filter bed In order to realize the separation of mud and water, the precipitated excess sludge is discharged into the anaerobic digestion tank for anaerobic digestion treatment, so that the excess sludge is reduced and the nitrogen and phosphorus nutrients in the microorganisms are released, and the water after sedimentation treatment flows into the distribution tank in turn and gravel packed filter bed; When the combined standard treatment mode is adopted, the influent flow distribution coefficient r _i of each level satisfies the following two formulas: [1] r ₀ +r ₁ +r ₂ +···r _n =1(n≥1), [2 】r _n =(a/b) ⁿ r ₀ , a is the amount of COD required to reduce NO ₃ -N to N ₂ , b is the ratio of influent COD/TN concentration; Under the combined standard treatment mode, black water enters the gray water treatment system to be mixed with gray water for treatment, and the gray water treatment system is switched to an efficient denitrification and phosphorus removal mode to ensure that the effluent COD, ammonia nitrogen, total nitrogen and total phosphorus are stable and reach Grade A emission standards. 2. the treatment method of domestic sewage in villages and towns according to claim 1, is characterized in that, the COD concentration in described black water is 150-650mg/L, and ammonia nitrogen concentration is 130-230mg/L, and total phosphorus concentration is 3-20mg /L, the potassium ion concentration is 100-300mg/L; the COD concentration of the gray water is 50-80mg/L, the ammonia nitrogen concentration is 5-10mg/L, the total nitrogen concentration is 5-15mg/L, and the total phosphorus concentration is 0.2-0.5mg/L; when the combined standard treatment mode is adopted, the influent COD concentration of the mixed sewage of black water and gray water is 100-300mg/L, the concentration of ammonia nitrogen is 35-90mg/L, and the concentration of total nitrogen is 35- 100mg/L, the total phosphorus concentration is 0.5-10mg/L. 3. The method for treating domestic sewage in villages and towns according to claim 1, characterized in that the filling height of the biochemical filler in the anaerobic digester accounts for 40-60% of the effective height of the anaerobic digester. 4. The method for treating domestic sewage in villages and towns according to claim 1, characterized in that, in the resource-based mode and the combined up-to-standard treatment mode, the treatment conditions of the anaerobic digester include a temperature of 10-40°C , The hydraulic retention time is 15-30 days. 5. The method for treating domestic sewage in villages and towns according to claim 1, characterized in that, when the quality-based recycling mode is adopted, all the aeration devices of the variable process biochemical tank are turned on, and the ash from the adjustment tank Water is introduced from the front end of the variable process biochemical pool, flows through each area in a push flow state, flows out from the last stage and flows into the sedimentation tank. 6. The method for treating domestic sewage in villages and towns according to claim 1, characterized in that, when the combined up-to-standard treatment mode is adopted, the aeration devices in each district of the variable process biochemical pool are sequentially pressed according to "open-close-open-close-open ..." to make the variable process into "aerobic + multi-stage anoxic/aerobic" operation, the mixed sewage from the regulating tank is respectively from the front end of the first aerobic zone and the anoxic zone of each level Introduced at the front end, it flows through each area in a push flow state, flows out from the last level of aerobic zone and flows into the sedimentation tank, and the last level of aerobic zone is equipped with a return pump to return to the last level of anoxic zone, and the return ratio is 100-300% . 7. The method for treating domestic sewage in villages and towns according to claim 1, characterized in that, when the material-based recycling mode is adopted, the treatment conditions of the sewage in the variable process biochemical pool include a temperature of 10-40°C, hydraulic retention The time is more than 4 hours; When the combined standard treatment mode is adopted, the treatment conditions of the water body in the variable process biochemical pool include a temperature of 10-40°C and a hydraulic retention time of more than 12h; In the separation of resources mode and combined standard treatment mode, the hydraulic retention time of sewage in the distribution pool of the variable process ecological filter bed is more than 0.5h, and the hydraulic retention time of the crushed stone filter bed is more than 10h. 8. The method for treating domestic sewage in villages and towns according to any one of claims 1-7, characterized in that, when the quality-based resource utilization mode is adopted, it is not necessary to add phosphorus removal to the water distribution tank of the variable process ecological filter bed Filter material bag: when adopting the combined standard treatment mode, it is necessary to add phosphorus removal filter material bag to the water distribution tank of the variable process ecological filter bed. 9. The method for treating domestic sewage in villages and towns according to any one of claims 1-7, characterized in that, the crushed stone packing filter bed adopts a design of more than two stages, and the direction of water flow is up and down, without soil covering, planting Canna, dry umbrella grass, windmill grass and mushroom grass are used as wetland green plants. 10. The method for treating domestic sewage in villages and towns according to claim 9, characterized in that the gravel-filled filter bed adopts a two-stage design.

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